Urchin-like iron oxide and a method for producing the urchin-like iron oxide

ABSTRACT

The present invention relates to an urchin-like iron oxide and a method for producing the urchin-like iron oxide. The urchin-like iron oxide comprises a core and multiple needle-like elongations protruded from the core. The needle-like elongations could be wire, rod, tube, cone, and flake. The length/width ratio of the needle-like elongation is high enough to apply in an optoelectronic field. The method in accordance with the present invention is to stably heat an iron-contained powder under room temperature by a thermal oxidation. The surface of the iron-contained powder is slow oxidized to form an urchin-like iron oxide with multiple uniform distributed needle-like elongations protruded from the surface. The size of each needle-like elongation is easily adjusted and changed by controlling the heating temperature. The method has advantages of simplified operation and lowered expense.

FIELD OF THE INVENTION

The present invention relates to an iron oxide and a method for producing the iron oxide, especially relates to an urchin-like iron oxide and a method for producing the urchin-like iron oxide

BACKGROUND OF THE INVENTION

Iron oxide, such as iron(III) oxide, is a popular material for producing an N-type semicomductor, has features of toxic-free property, light stability, and great shield capability and is widely applied in coating, catalytic, electrochemical and bioengineering fields. However, the electrochemical properties of iron oxide will be significantly affected by the particle size, pore structure and form of an iron oxide particle.

The iron oxide particle might be spheral shaped with nano or micro scale. Some researchers also try to produce screw or urchin-like shaped iron oxide. Methods for producing specific iron oxides include a hydrothermal synthesis and a template technique. The hydrothermal synthesis uses a metallic oxide to form a metal-surfactant precursor by reacting with a surfactant under a water-free environment. Then the metal-surfactant precursor is acted with a additive and some water so that the surfactant is self-arranged spontaneously and the metallic oxide undergoes a hydrolysis and poly-condensation process to form an urchin-like iron oxide (Du and Cao, 2008). The template technique uses a micro spheral-shaped sulfonate polystyrene as a hard template. The sulfonate polystyrene reacts with an iron-contained solution in a hydrothermal condition to form a urchin-shaped iron oxide. The final step is to remove the template by a sintering process.

The urchin-like iron oxides in accordance with the above mentioned methods just have urchin-shaped in geometry without uniform needle-arrangement. Otherwise, the process of the hydrothermal synthesis and the template formation of the template technique are highly complexity so that the production cost will be increased. The above two methods also have disadvantage of limiting operation requirement such as specific atmosphere controlled or solution formulated. Accordingly, it is difficult to precisely control multiple parameters of the iron oxide and to form a standardized urchin-like product.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an inventive urchin-like iron oxide. The urchin-like iron oxide comprises an iron core has a surface and multiple needle-like elongations that are mounted on protruded form the surface of the iron core. The iron core is a fine powder and has nano scale in diameter. The needle-like elongation has high length and width ratio and could be broadly used in the electro-optical engineering and the catalytic field.

Another object of the present invention is to provide a method for producing an urchin-like iron oxide. The method has advantages of simplified operation and lowered expense. The method in accordance with the present invention is to stably heat an iron-contained powder under room temperature by a thermal oxidation. The surface of the iron-contained powder is slow oxidized to form an urchin-like iron oxide with multiple uniform distributed needle-like elongations protruded from the surface. The size of each needle-like elongation is easily adjusted and changed by controlling the heating temperature. The crystallized feature, length, diameter and appearance of the needle-like elongations of the urchin-like iron oxide are uniform. The ratio of the length and width of the needle-like elongation is higher that is suitable for applying in an optoelectronic field.

The above objects and advantages of the present invention will become more readily apparent to those ordinarily skilled in the art after reviewing the following detailed descriptions and accompanying drawings in which:

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is structure of an urchin-like iron oxide in accordance with the present invention.

FIG. 2 is a flow chart to show a method for producing an urchin-like iron oxide in accordance with the present invention.

FIG. 3A is a scanning electron microscopy graph of a first embodiment shows appearance of an iron powder that is heated to 300° C.

FIG. 3B is a scanning electron microscopy graph of the first embodiment shows appearance of an iron powder that is heated to 300° C. for half hour.

FIG. 3C is a scanning electron microscopy graph of the first embodiment shows appearance of an iron powder that is heated to 300° C. for an hour.

FIG. 3D is a scanning electron microscopy graph of the first embodiment shows appearance of an iron powder that is heated to 300° C. for 10 hours.

FIG. 4A is a scanning electron microscopy graph of a second embodiment shows appearance of an iron powder that is heated to 350° C.

FIG. 4B is a scanning electron microscopy graph of the second embodiment shows appearance of an iron powder that is heated to 350° C. for an hour.

FIG. 4C is a scanning electron microscopy graph of the second embodiment shows appearance of an iron powder that is heated to 350° C. for eight hours.

FIG. 5A is a scanning electron microscopy graph of a second embodiment shows appearance of an iron powder that is heated to 400° C.

FIG. 5B is a scanning electron microscopy graph of the second embodiment shows appearance of an iron powder that is heated to 400° C. for half hour.

FIG. 5C is a scanning electron microscopy graph of the second embodiment shows appearance of an iron powder that is heated to 400° C. for six hours.

FIG. 6 is an X-ray diffraction diagram of the urchin-like iron oxide in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Please refer to FIG. 1, an urchin-like iron oxide (1) in accordance with the present invention comprises an iron core (11) and multiple needle-like elongations (12). The iron core (11) is sphere and has a surface. The needle-like elongations (12) are well, radically and radiated mounted on the surface of the iron core (11). The needle-like elongations (12) could be wire, rod, tube, cone, or flake. Each needle-like elongations (12) has a top portion (111) and a connected portion (112) and has length at least 50 nanometer. The top portion (111) is protruded form the surface and is at least 5 nanometers in diameter. The bottom portion (122) is mounted and conjugated on the surface of the iron core and is at least 10 nanometers in width.

With reference to FIG. 2, a method for producing an urchin-like iron oxide in accordance with the present invention comprises steps of:

providing a raw material (20): providing an iron-contained fine powder as the raw material;

heating and oxidation (21) the raw material: putting the iron-contained fine powder on a plate and heating the iron-contained fine powder to a specific temperature for a period.

In the heating and oxidation (21) step, the raw material is heated from room temperature to at least 220° C. for at least half hour, preferably the heating rate is 1 to 20° C. per minute. In one embodiment, the heating and oxidation (21) step is operated under atmosphere without applying a specific condition. In another embodiment, the heating and oxidation (21) step is operated under the oxygen concentration by at least 10 mole percentages.

Example 1

The example 1 uses an iron powder as the raw material that is heated to 300° C. with the temperature is increased by 5° C. per minute. With reference to FIGS. 3A to 3D, after heated with 300° C. for 30 minutes, the surface of the iron powder is started to oxidation. After 2 hours, the surface of the iron powder is disposed with a layer of oxide and starts to grow multiple tiny protrudes with a top portion is 10 to 20 nanometers in diameter. While heating to 10 hours, the protrudes of the surface of the iron powder are extended to form an urchin-like iron oxide particle with multiple needle-like elongations. In the embodiment, the needle-like elongation has a top portion and a connected portion. The length of the needle-like elongation is between 1.8 to 2.2 micrometers. The diameter of the top portion of each needle-like elongation is 20 to 30 nanometers. A ratio of the diameter of the top portion and the length of the needle-like elongation is about 86. Also, in this embodiment, the oxide is increased by 0.26% per minute.

Example 2

The example 2 uses an iron powder as the raw material that is heated to 350° C. with the temperature is increased by 5° C. per minute and then keeps heating by 350° C. for a period. With reference to FIGS. 4A to 4C, while staring to heat the iron powder from room temperature for 30 minutes, the surface of the iron powder starts to produce an oxide. After heating for an hour, the surface of the iron powder is disposed by layer of oxide with multiple tiny needle-like elongations that the top portion is 20 to 30 nanometers in diameter. Once heating for 8 hours, the length and the diameter of the top portion of each needle-like elongation is about 1.8 to 2.2 micrometers and 30 to 50 nanometers respectively. Therefore, a ratio of the diameter of the top portion and the length of the needle-like elongation is about 53, and the oxide is increased by 0.26% per minute.

Example 3

The example 3 also uses an iron powder as the raw material that is heated to 400° C. with the temperature is increased by 5° C. per minute and then keeps heating by 400° C. for a period. With reference to FIGS. 5A to 5C, while staring to heat the iron powder from room temperature for 30 minutes, the surface of the iron powder starts to produce multiple needle-like oxides and each oxide has a top portion with 40 to 60 nanometers in diameter. After heating for six hours, the surface of the iron powder is disposed by multiple tiny needle-like elongations and has urchin-like appearance. In the sample 2, each needle-like elongation is about 1.8 to 2.2 micrometers and 60 to 100 nanometers respectively. Therefore, a ratio of the diameter of the top portion and the length of the needle-like elongation is about 26, and the oxide is increased by 1.24% per minute.

Example 4

With refer to FIG. 6, an X-ray diffraction diagram of the urchin-like iron oxide in accordance with the present invention indicates the urchin-like iron oxide comprises alpha-iron(II) oxide, iron(III) oxide and alpha-iron. There are many needle-like elongations disposed on the surface of the iron particle, therefore the lattice planes with Miller indices (110) has higher intensity than others. Otherwise, a peak (star symbol) shown at 45 degrees indicates the iron particle does not oxidation completely.

With reference to FIGS. 3A˜3D, 4A˜4C and 5A˜5C, while keeping to heat the iron particles with a stable temperature, the surface of the iron particle is starting to react with air and produces a lot of iron oxides (such as iron(II) oxide or iron(III) oxide). With the heating period increased, the oxide is delaminated by different kind of oxide. The outer layered oxide is directly contacted and reacted with air. At a lower heating temperature, the oxidation rate of the outer layered oxide is slower than at a higher heating temperature so that the oxide are tightly arranged on the surface of the iron powder.

Accordingly, the method for producing an urchin-like iron oxide in accordance with the present invention has advantage of easy operation and efficiently decreases the operation expense and procedure. The ratio of the length and width of the needle-like elongation of the urchin-like iron oxide is higher for applying in an optoelectronic field. 

1. An urchin-like iron oxide, comprising: a core, being an iron powder and have a surface; and multiple needle-like elongations, being radically and radiated mounted on the surface of the iron core and having a top portion protruded form the surface and a connected portion mounted and conjugated on the surface of the core.
 2. The needle-like elongations as claimed in claim 1, wherein the needle-like elongations are wire, rod, tube, cone, or flake.
 3. The urchin-like iron oxide as claimed in claim 1, wherein each needle-like elongation being at least 50 nanometers in length.
 4. The urchin-like iron oxide as claimed in claim 3, wherein the top portion of each needle-like elongation being at least 5 nanometers in diameter.
 5. The urchin-like iron oxide as claimed in claim 4, wherein the connected portion having a bottom is at least 30 nanometers in width.
 6. A method for producing an urchin-like iron oxide comprising steps as following: providing a raw material: providing a grinded iron-contained powder; and heating and oxidation: putting the iron-contained powder on a plate and heating the iron-contained powder by a stable temperature for a period.
 7. The method for producing an urchin-like iron oxide as claimed in claim 6, wherein the temperature being at least 220° C.
 8. The method for producing an urchin-like iron oxide as claimed in claim 7, wherein the heating step form room temperature to the stable temperature being increased by 1 to 20° C. per minute.
 9. The method for producing an urchin-like iron oxide as claimed in claim 8, wherein the iron-contained powder being heated for at least half hour.
 10. The method for producing an urchin-like iron oxide as claimed in claim 9, wherein the heating and oxidation step having a oxidation rate by an oxide is increased 0.2 to 1.5 wt %.
 11. The method for producing an urchin-like iron oxide as claimed in claim 10, wherein the heating and oxidation step being operated under an atmosphere condition or an oxygen concentration by at least 10 mole percentages. 